It is known in the art relating to internal combustion engines that operating efficiency may be improved and heat loss from the combustion and exhaust gases may be limited by applying insulating coatings or inserts to the working gas exposed surfaces. Nevertheless, while the prior art shows numerous examples of proposals for accomplishing such purposes, these proposals have not, for the most part, evolved into practical commercial constructions. However, the need for such constructions exists in order to obtain higher engine efficiencies, control exhaust emissions and limit the size of external cooling system required for a given engine horsepower output.